(a) Technical Field
The present invention relates to a porous separator for a fuel cell. More particularly, the present invention relates to a porous separator that has a shape that induces a turbulent to flow of reactant gases and has an improved structure with excellent workability.
(b) Background Art
Referring to FIG. 6 that shows the conventional structure of a fuel cell stack, a Membrane-Electrode Assembly (MEA) is disposed in the middle of the fuel cell stack. The MEA includes a polymer electrolyte membrane 10 that allows hydrogen protons to pass through, and a cathode 12 and an anode 14 that are catalyst layers coated on the both sides of electrolyte membranes such that hydrogen and oxygen react with each other.
Also, gas diffusion layers (GDL) 16 are stacked on the outer sides of the electrode membrane, i.e., the cathode 12 and anode 14, and separators 20 with a flow field formed therein are disposed on the outer sides of the gas diffusion layer 16 to provide fuel and discharge water generated from a reaction while allowing a gasket 18 to be interposed between the separators 20. An end plate 30 is disposed at the outermost side of the fuel cell stack to support and fix the above components.
Within the anode 14 of the fuel cell stack an oxidization reaction of hydrogen is performed to generate protons and electrons, which move to the cathode 12 through the polymer electrolyte membrane 10 and the separator 20, respectively. Protons, electrons from the anode 14, and oxygen in the air electrochemically react in the cathode 12 to generate water, and simultaneously electrical energy is generated from the flow of electrons.
Generally, the separator 20 may have a structure in which lands (closely supported by the gas diffusion layer and channels (flow field) serving as a flow path of a fluid) are repeatedly disposed. Specifically, since a typical separator has a structure in which lands and channels (flow field) are repeatedly curved, a channel on one side facing the gas diffusion layer is utilized as a space in which reactant gases such as hydrogen and air flow, and a channel on the opposite side is utilized as a space in which cooling water flows. Accordingly, one unit cell may include two separators, one separator that has a channel for hydrogen/cooling water and the other separator that has a channel for oxygen/cooling water.
For example, Korean Patent Application Publication No. 10-2011-0091520 (filed on Sep. 9, 2011) teaches a porous separator in which reactant gases form a turbulent flow and are more easily diffused into a gas diffusion layer than a typical separator. Hereinafter, a detailed description thereof will be made with reference to FIG. 5 and FIG. 6.
In the above patent application, a plurality of flow apertures are formed on a metal plate using an etching process, and then the pressing process is performed using a mold having an embossed shape in which a protruded portion and a recessed portion are repeatedly formed. As shown in FIG. 5, the porous separator 20 manufactured by such a process has a plurality of flow apertures 23 arranged in a zigzag pattern and penetrating therethrough. Also, the protruded portion 21 closely adhered to a flat plate 24 and the recessed portion 22 closely adhered to the gas diffusion layer 16 adjacent to the anode 14 or the cathode 12 are formed in a zigzag pattern.
In this case, the flat plate 24 serves as a sealing partition for a hydrogen or oxygen channel, and a space between a flat plate 24 included in one cell and a flat plate 24 included in another cell becomes a cooling water channel that is sealed by gaskets, etc. Accordingly, reactant gases may flow in the vertical and horizontal directions along the protruded portion and the recessed portion while passing through the flow aperture of the porous separator, causing a turbulent flow to the reactant gases. By delivering the reactant gases to the gas diffusion layer in a turbulent flow, the diffusion of the reactant gases increases as a result, thereby improving the performance of the fuel cell.
However, since in this above described porous separator, not only the flow apertures but also the protruded portions and the recessed portions are formed in a zigzag pattern, the overall shape and structure of the porous separator are very complicated, resulting in a more difficult manufacturing press mold and higher costs for production. Thus, a more simplistic design that provides similar results is greatly needed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.